This invention provides tools for facilitating removal of a cylinder head of an overhead cam engine and for facilitating cranking of the engine when the cylinder head is removed.
The job of overhauling an automobile engine is time-consuming and costly to the automobile owner. The job of disassembling and reassembling certain automobile engines is especially tedious and time-consuming when there are no tools available to aid the repairman in accomplishing certain necessary steps in the repair process. For example, to remove the cylinder head of an overhead cam engine manufactured by Nissan Motor Company, Ltd., Tokyo, Japan (Datsun), or other similar engines, the timing chain is initially removed to free the cam shaft sprocket. The sprocket is then removed so that the cylinder head can be removed. The timing chain must be supported while the cam shaft sprocket is removed to prevent the timing chain from slipping off the crankshaft sprocket. Service manuals for such an engine recommend placing a wood block in the timing chain housing to support the timing chain on the crankshaft sprocket. Often a repairman will make such a wood block to hopefully match the approximate dimensions of the space above the crankshaft sprocket between opposite portions of the timing chain. Such a device has proved very unreliable in holding the timing chain on the crankshaft sprocket. A chain tensioner in the lower portion of the timing chain housing normally applies spring loaded tension against the side of the timing chain. If there is any slack in the chain, the chain tensioner will pop the chain off the crankshaft sprocket. When such a wood block is inserted into the timing chain housing it often leaves too much slack on the timing chain and the chain tensioner pops the chain off the crankshaft sprocket. Once the timing chain is lost, a substantial amount of additional labor is required. This can require removal of the timing chain cover, the radiator, water pump, and smog control equipment in order to obtain access for replacing the tensioner in its proper position and properly aligning the timing marks for the timing chain.
When the wood block is in place in the timing chain housing, the engine cannot be cranked or the timing chain will slip off the crankshaft sprocket. It is necessary to crank the engine when removing the pistons from the engine block in order to obtain access to the piston connecting rods and the rod bearings. It is common practice for repairmen to remove the engine block from the vehicle to obtain access to the piston connecting rods and the rod bearings.
The present invention provides a tool which can be inserted into the timing chain housing for supporting the timing chain while the cam shaft sprocket is removed. The tool can be actuated to oppose the normal bias of the chain tensioner so that the chain tensioner will not tend to pop the timing chain off the crankshaft sprocket while the timing chain is being supported.
The present invention also provides a cam shaft idler tool for supporting the cam shaft sprocket after the cylinder head has been removed. The cam shaft idler supports the cam shaft sprocket on the timing chain and allows the engine to be cranked, while preventing the timing chain from slipping off the crankshaft sprocket. Thus, the repairman can crank the engine to obtain access to the piston connecting rods and rod bearings while the cylinder head is removed and without requiring removal of the engine block.